Physical and Chemical Properties of MoP, Ni2P, and MoNiP Hydrodesulfurization Catalysts:  Time-Resolved X-ray Diffraction, Density Functional, and Hydrodesulfurization Activity Studies

• Published in: The journal of physical chemistry. B Vol. 107; no. 26; pp. 6276 - 6285
• Main Authors: Rodriguez, José A, Kim, Jae-Yong, Hanson, Jonathan C, Sawhill, Stephanie J, Bussell, Mark E
• Format: Journal Article
• Language: English
• Published: American Chemical Society 03-07-2003
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp022639q

Synchrotron-based time-resolved X-ray diffraction was used to study in situ the crystalline phases present during the preparation of bulk and silica-supported MoP, Ni2P, and MoNiP by reduction of oxidic precursors in hydrogen. Independent of the type of oxidic precursor used or the presence of silica as a support, the formation of the metal phosphides occurs at temperatures between 600 and 800 °C. Since the common species in all the cases are phosphate-type groups (PO x ), it seems that their reduction by hydrogen is the final and determining step in the formation of MoP, Ni2P, and MoNiP. Silica-stabilized phosphide phases were detected during the synthesis of Ni2P/SiO2 and MoP/SiO2 catalysts. In the case of Ni2P/SiO2, before the appearance of the final phosphide, strong diffraction lines are observed for Ni12P5. First-principles density functional calculations for bulk MoP, Ni2P, and MoNiP indicate that the Ni−P and Mo−P bonds in these compounds have a small degree of ionic character. For MoP, Ni2P, and MoS2 a correlation is found between the electronic properties of the metal cations and their hydrodesulfurization activities when supported on silica. Surprisingly, a MoNiP/SiO2 catalyst is much less active than either MoP/SiO2 or Ni2P/SiO2 catalysts.